Die and method for preparing optical aluminum alloy through twisting extrusion severe plastic deformation and application

Abstract

The invention belongs to the technical field of aluminum alloy plastic forming, and discloses a mold base for preparing optical aluminum alloy through twisting extrusion severe plastic deformation, and a first discharging channel and a second discharging channel are formed in the base; the core mold sleeve and the core mold are arranged in a matched mode and are arranged on the base, a forward core mold and a reverse core mold which are communicated with the first discharging channel and the second discharging channel are arranged in the core mold, and the forward core mold and the reverse core mold comprise spiral cylindrical channels with the same diameter; the upper die is arranged at the tops of the core die sleeve and the core die; the extrusion rod seat assembly comprises an extrusion rod seat arranged at the top of the upper die, a first extrusion rod and a second extrusion rod; the extrusion rod base and the upper die are provided with a first twisting and extruding channel and a second twisting and extruding channel which are communicated with the forward core die and the reverse core die respectively, and the first extrusion rod and the second extrusion rod move up and down in the first twisting and extruding channel and the second twisting and extruding channel correspondingly to extrude a blank to be machined. The invention further provides a preparation method and application. The die, the method and the application have the characteristics of high efficiency, low cost and high precision.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum alloy plastic forming, and specifically relates to a mold, a method and an application for preparing optical aluminum alloy by twisting, extruding and large plastic deformation. Background Art

[0002] Optical aluminum alloy is a key material for the preparation of precision optical reflectors such as missile seekers, optoelectronic pods, satellite cameras, and automotive laser radars. The higher the surface processing accuracy of the reflector, the better the imaging quality of the optical instrument can be guaranteed. In order to improve the processing accuracy of optical reflectors, the reflector material structure is required to be ultra-fine and uniform.

[0003] The surface processing accuracy of reflectors for high-end aerospace equipment is extremely high, usually within 3nm, or even within 1nm. The Netherlands is the most advanced supplier of optical microcrystalline aluminum reflector materials in the world. It uses rapid solidification belt spinning method and hot isostatic pressing to prepare optical microcrystalline aluminum materials. The surface processing accuracy Ra value of the reflector has reached 1nm, and the specification has reached Φ1000mm. At present, my country's detection and guidance high-end optical reflector materials rely on imports, and large-scale foreign microcrystalline aluminum materials are prohibited from being exported to my country, which has become an urgent problem to be solved in the defense industry.

[0004] At present, the optical reflectors of domestic automotive laser radars have problems such as coarse grains, uneven structure, and many impurities. The processed reflectors have problems such as poor processing accuracy, unstable quality, and low yield. Automotive reflectors are often processed with imported American aluminum plates, which have good material consistency, but there are still problems such as low processing accuracy and unsatisfactory quality caused by many impurities. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background technology and provide a mold, method and application for preparing optical aluminum alloy by twisting extrusion and large plastic deformation with high efficiency, low cost and high precision.

[0006] In order to solve the above technical problems, the technical solution proposed by the present invention is: a mold for preparing optical aluminum alloy by twisting extrusion and large plastic deformation, comprising: A base, wherein a first discharge channel and a second discharge channel are formed on the base; The core mold sleeve and the core mold are arranged on the base, and the core mold is provided with a forward core mold and a reverse core mold which are connected with the first discharge channel and the second discharge channel. The forward core mold and the reverse core mold include spiral cylindrical channels with equal diameters, and the spiral directions of the forward core mold and the reverse core mold are opposite to offset the lateral force; An upper mold is arranged on the top of the core mold sleeve and the core mold; The extrusion rod seat assembly includes an extrusion rod seat and a first extrusion rod and a second extrusion rod arranged on the top of the upper mold; the extrusion rod seat and the upper mold are provided with a first extrusion channel and a second extrusion channel which are respectively connected to the forward core mold and the reverse core mold, and the first extrusion rod and the second extrusion rod move up and down in the first extrusion channel and the second extrusion channel to extrude the blank to be processed.

[0007] In one embodiment, the base circle diameter of the spiral cylindrical channel of the forward core mold and the reverse core mold is 15mm~22mm, the pitch is 110mm~140mm, the helix angle is 18.6°~24.5°, and the number of spiral turns is 0.5-1.

[0008] In one embodiment, the spiral cylindrical channel includes a transition section connected to the upper and lower channels and an equal spiral section located between the two transition sections.

[0009] In one embodiment, the forward core mold and the reverse core mold are inverted cone shapes, the shape of the core mold sleeve matches the forward core mold and the reverse core mold, and the forward core mold and the reverse core mold are fixed to the core mold sleeve by flat keys.

[0010] In one embodiment, there is a 1-2 mm gap between the forward core mold and the reverse core mold and the base, and the forward core mold and the reverse core mold are in contact with the upper mold.

[0011] Based on the same inventive concept, a method for preparing an optical aluminum alloy using the mold as described above is provided, comprising: Firstly, the blank is placed into the first extrusion channel and the second extrusion channel respectively; The blank is twisted and deformed in the spiral channel of the core mold by pressing down the extrusion rod, and the deformed blank is taken out from the outlets of the first discharge channel and the second discharge channel on the base; The deformed billet is put back into the first torsional extrusion channel and the second torsional extrusion channel, and the billet is pressed down again by the extrusion rod to cause torsional extrusion deformation in the spiral channel of the core mold. The torsional extrusion deformation operation is repeated to obtain an optical aluminum alloy product with large torsional plastic deformation. The billet diameter remains unchanged during the repeated operation.

[0012] In one embodiment, before the blank is loaded into the mold, a release agent is evenly applied to the surface of the blank and then heated to a temperature of 250±10°C, and at the same time the mold is heated to a temperature of 250±10°C; or Before the blank is loaded into the mold, a release agent is evenly applied on the surface of the blank and then heated to a temperature of 400-550°C, and at the same time the mold is heated to a temperature of 400-550°C.

[0013] In one embodiment, before the blank is loaded into the mold, the mold and the blank are cooled to the temperature of liquid nitrogen, and the twisting and extruding deformation operation is repeated for more than 6 times for one blank.

[0014] In one embodiment, when the extrusion rod presses down to extrude the billet and cannot provide force on the current billet, the extrusion rod is removed, and new billets are loaded into the first extrusion channel and the second extrusion channel, and then the new billet is pressed down by the extrusion rod, and the new billet is used to extrude the previous billet out of the mold.

[0015] Based on the same inventive concept, there is provided a product obtained by the method for preparing an optical aluminum alloy as described above and its application in an optical reflector.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: compared with the prior art multi-directional forging large plastic deformation method, the mold and method for preparing optical aluminum alloy by twisting and extruding large plastic deformation provided by the present invention, by setting a forward core mold and an inverse core mold in the core mold, and pressing the extrusion rod down in a spiral cylindrical channel with equal diameter to obtain an aluminum alloy product with large plastic deformation, the production efficiency is high, the shape of the mirror blank is consistent with the final reflector product, both are circular, the material utilization rate is high, the processing allowance is small, and the blank is in a three-dimensional compressive stress state during forming, which can effectively reduce the risk of cracking and improve the yield rate. At the same time, the implementation plan is simple, the single strain reaches 2.0, and large plastic deformation can be quickly achieved with high efficiency. Furthermore, in the mold and method of the present invention, different twisting and extrusion forming schemes can be formulated according to product quality requirements to improve efficiency and control costs. For optical aluminum alloys with ordinary processing quality requirements, such as processing quality at the level of 5-10nm, 250℃ warm extrusion or 400-550℃ hot extrusion can be used, and the number of extrusions can be 1-3 times; for optical aluminum alloys with higher processing quality requirements, such as processing quality at the level of 2-5nm, room temperature extrusion or 200-250℃ warm extrusion can be used, and the number of extrusion passes can be 3-6 times; by lowering the extrusion forming temperature, although the energy consumption is higher, by increasing the number of extrusion deformations, a finer structure can be obtained, thereby improving the surface processing quality of the mirror blank; for optical aluminum alloys with ultra-high processing quality requirements, such as processing quality at the level of 1-2nm or less than 1nm, deep cold extrusion can be used. Before extrusion forming, the mold and the blank are cooled to liquid nitrogen temperature, and the number of extrusion passes is greater than 6 times to prepare nano-level ultrafine grain structure, and the product processing quality can reach sub-nanometer level. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 A schematic diagram of a mold structure for preparing optical aluminum alloy by torsional extrusion and large plastic deformation according to an embodiment; Figure 2 A schematic diagram of the structure of a mold portion for preparing an optical aluminum alloy by twisting extrusion and large plastic deformation according to an embodiment; Figure 3 A schematic diagram of a mold structure for preparing optical aluminum alloy by torsional extrusion and large plastic deformation according to an embodiment; Figure 4 is a schematic diagram of twisting channel parameters in one embodiment; Figure 5 is the strain field distribution under different process parameter conditions of an implementation method; Figure 6 This is a schematic diagram of a deformation condition of a channel in Example 4 of the present application; Figure 7 This is a schematic diagram of the deformation of one pass in comparative example 1; Figure 8 This is a schematic diagram of the deformation of one pass in comparative example 2. DETAILED DESCRIPTION

[0019] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and preferred embodiments of the present invention, but the protection scope of the present invention is not limited to the following specific embodiments.

[0020] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0021] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0022] See also Figure 1-8 , a die for preparing optical aluminum alloy by twisting extrusion and large plastic deformation in one embodiment, from top to bottom, includes an extrusion rod seat assembly, an upper die 3, a sleeved core die sleeve 4 and a core die, and a bottom die 7, wherein the extrusion rod seat assembly includes an extrusion rod seat 1 and an extrusion rod 2. The core die includes a straight core die 6 and an inverse core die 5. Specifically, a first discharge channel and a second discharge channel are opened on the base 7; the first discharge channel and the second discharge channel are connected to the straight core die 6 and the inverse core die 5 respectively. The straight core die 6 and the inverse core die 5 include spiral cylindrical channels with equal diameters, and the spiral directions of the straight core die 6 and the inverse core die 5 are opposite to offset the lateral force. The extrusion rod 2 includes a first extrusion rod and a second extrusion rod; the extrusion rod seat and the upper die are opened with a first twisting channel and a second twisting channel connected to the straight core die 6 and the inverse core die 5 respectively, and the first extrusion rod and the second extrusion rod are correspondingly movable up and down in the first twisting channel and the second twisting channel to extrude the blank to be processed.

[0023] Preferably, in one embodiment, the base diameter of the spiral cylindrical channel of the forward core mold 6 and the reverse core mold 5 is 15mm-22mm, the pitch is 110mm-140mm, the helix angle is 18.6°-24.5°, and the number of spiral turns is 0.5-1. The present invention uses finite element simulation to perform a large number of simulation optimizations on the spiral cylindrical channel. Taking the experimental results into consideration, within the above parameter range, a more uniform and sufficient deformation can be obtained, while the forming load is small, the channel height is short, the mold structure is more reasonable, and the implementation is convenient.

[0024] Preferably, the spiral cylindrical channel includes a transition section connected to the upper and lower channels and an equal spiral section located in the middle, so as to achieve a smooth transition of the spiral channel, and the feed port and the discharge port are on the same axis to obtain uniform deformation. Figure 4 .

[0025] Preferably, in one embodiment, the forward core mold 6 and the reverse core mold 5 are fixed to the core mold sleeve by a flat key 8 to prevent axial rotation.

[0026] Preferably, in one embodiment, the forward core mold 6 and the reverse core mold 5 are inverted cones, and the shape of the core mold sleeve 4 matches the forward core mold 6 and the reverse core mold 5 to play a fixing role during the forming process.

[0027] Preferably, in one embodiment, there is a 1-2 mm gap between the forward core mold 6 and the reverse core mold 5 and the base 7, so that the forward core mold 6 and the reverse core mold 5 are fitted with the upper mold 3 during operation, eliminating the gap at the joint surface between the core mold and the upper mold, and putting the core mold in a compressive stress state to improve the stress state of the mold.

[0028] The components connected to each other among the extrusion rod seat assembly, the upper mold 3, the sleeved core mold sleeve 4, and the core mold and the bottom mold 7 are connected by connecting bolts, and the connection method is simple and the disassembly and assembly are convenient.

[0029] Based on the same inventive concept, a method for preparing an optical aluminum alloy using the mold as described above is provided, comprising: S10, firstly put the blank into the first extrusion channel and the second extrusion channel respectively.

[0030] Preferably, before placing the blank into the first extrusion channel and the second extrusion channel, oil-based lubricant is first applied to the first discharge channel, the second discharge channel, the first extrusion channel, the second extrusion channel, the forward core mold 6 and the reverse core mold 5. Preferably, high-temperature grease is applied to the outer surfaces of the forward core mold 6 and the reverse core mold 5 that match the core mold sleeve 4. Then, the forward core mold 6 and the reverse core mold 5 are installed in the core mold sleeve 4, and then installed with the upper mold 3 and the bottom mold 7 in sequence.

[0031] Specifically, during pressing, a cushion block is placed on the top of the extrusion rod seat 1, and the punch is dropped in a pressure-free mode to contact the cushion block. The height of the press slide at this time is recorded, and after calculating the lower limit position of pressing, the cushion block is removed and the press is lifted to the upper limit position.

[0032] In one embodiment, before the blank is loaded into the mold, a release agent is evenly applied to the surface of the blank and then heated to a blank temperature of 250±10°C, and at the same time the mold is heated to a temperature of 250±10°C; or.

[0033] Before the blank is loaded into the mold, a release agent is evenly applied on the surface of the blank and then heated to a temperature of 400-550°C, and at the same time the mold is heated to a temperature of 400-550°C.

[0034] In one embodiment, before the blank is loaded into the mold, both the mold and the blank are cooled to liquid nitrogen temperature.

[0035] S20, the blank is pressed downward by the extrusion rod 2 so as to be twisted and deformed in the spiral channel of the core mold, and the deformed blank is taken out from the outlets of the first discharge channel and the second discharge channel on the base 7.

[0036] The extrusion rod 2 is extruded at a forging speed of 1 mm / s, and is under-pressed by 2 mm at the calculated lower limit position. The load data on the press display during the forging process is recorded, and the press is slowly lifted after the pressing is completed.

[0037] S30, putting the deformed billet back into the first torsion channel and the second torsion channel, pressing down again by the extrusion rod 2 so that the billet undergoes torsion deformation in the spiral channel of the core mold, repeating the torsion deformation operation to obtain an optical aluminum alloy product with large plastic deformation, and the billet diameter remains unchanged during the repeated operation.

[0038] Preferably, in one embodiment, when the extrusion rod presses down to extrude the billet and cannot provide force on the current billet, the extrusion rod is removed, and new billets are loaded into the first extrusion channel and the second extrusion channel, and then the new billet is pressed down by the extrusion rod, and the new billet is used to extrude the previous billet out of the mold.

[0039] That is to say, one complete extrusion operation can complete the forming of 4 cylindrical aluminum alloy products.

[0040] Preferably, according to different product requirements, the mold and the blank are subjected to different temperature treatments before extrusion, as follows: 1) For optical aluminum alloys with ordinary processing quality requirements, such as processing quality of 5-10nm level, 250℃ warm extrusion or 400-550℃ hot extrusion can be used, and the number of extrusions can be 1-3 times; 2) For optical aluminum alloys with higher processing quality requirements, such as processing quality at the level of 2-5nm, room temperature extrusion or 200-250℃ extrusion can be used, and the number of extrusions can be 3-6 times; by lowering the extrusion forming temperature and increasing the number of deformations, a finer structure can be obtained, and the surface processing quality of the mirror blank can be improved, but at the same time, the energy consumption is higher; 3) For optical aluminum alloys with ultra-high processing quality requirements, such as processing quality of 1-2nm or less than 1nm, deep cold extrusion can be used. Before extrusion, the mold and the billet are cooled to liquid nitrogen temperature. The number of extrusions is greater than 6 times to prepare nano-scale ultrafine grains. The product processing quality can reach sub-nanometer level.

[0041] Preferably, after forming, the blank is subjected to solid solution and aging heat treatment to obtain the desired optical reflector blank material.

[0042] In one embodiment, the product obtained by the method for preparing an optical aluminum alloy as described above can be used in an optical reflector.

[0043] Specifically, different parameters are set according to Table 1 below to obtain the strain performance results of aluminum alloy products. Figure 5 The strain field distribution of Examples 1 to 4 is shown in Table 1. According to the results in Table 1, the result of Example 4 is the best, and the average strain and maximum strain of the obtained product are both large. Figure 5 The results show that the strain field distributions of the four embodiments are very uniform. The average strain and maximum strain of embodiments 1 to 3 are also within a preferred range.

[0044] Table 1 Strain results of products obtained under different parameter conditions

[0045] Comparative Example 1: Multi-directional forging: The deformation of a single forging is 40%, and one upsetting and one pulling is one pass. Figure 7 As shown. The maximum strain is 2.72, the minimum strain is 0.85, and the average strain is 1.55. Conventional hot forging large plastic deformation often uses multi-directional forging. For example, the commonly used multi-directional forging process requires four upsets and three draws, and its process flow is long and requires 12 compression deformations. The present invention only needs one twisting and extrusion to achieve the deformation of four upsets and three draws in multi-directional forging.

[0046] Comparative Example 2: Deep cold multi-directional compression, single deformation amount 20%, one compression in each of three orthogonal directions is one pass. The deformation of one pass is as follows Figure 8 As shown, the maximum strain is 2.03, the minimum strain is 0.53, and the average strain is 0.96. Conventional cryogenic multi-directional compression requires three passes, that is, 9 compressions. The effect obtained by the present invention only requires one torsional deformation, which can exceed three passes of cryogenic multi-directional compression.

[0047] Compared with the prior art, the beneficial effects of the present invention are as follows: compared with the prior art multi-directional forging large plastic deformation method, the mold and method for preparing optical aluminum alloy by twisting and extruding large plastic deformation provided by the present invention, by setting a forward core mold 6 and an inverse core mold 5 in the core mold, and pressing the extrusion rod 2 down in a spiral cylindrical channel with equal diameter to obtain an aluminum alloy product with large plastic deformation, the production efficiency is high, the shape of the mirror blank is consistent with the final reflector product, both are circular, the material utilization rate is high, the processing allowance is small, and the blank is in a three-dimensional compressive stress state during forming, which can effectively reduce the risk of cracking and improve the yield rate. At the same time, the implementation plan is simple, the single strain reaches 2.0, and large plastic deformation can be quickly achieved with high efficiency. Furthermore, in the mold and method of the present invention, different twisting and extrusion forming schemes can be formulated according to product quality requirements to improve efficiency and control costs. For optical aluminum with ordinary processing quality requirements, such as processing quality at the level of 5-10nm, 250℃ warm extrusion or 400-550℃ hot extrusion can be used, and the number of extrusions can be 1-3 times; for optical aluminum alloys with higher processing quality requirements, such as processing quality at the level of 2-5nm, room temperature extrusion or 200-250℃ warm extrusion can be used, and the number of extrusion passes can be 3-6 times; by lowering the extrusion forming temperature, although the energy consumption is higher, by increasing the number of extrusion deformations, a finer structure can be obtained, thereby improving the surface processing quality of the mirror blank; for optical aluminum alloys with ultra-high processing quality requirements, such as processing quality at the level of 1-2nm or less than 1nm, deep cold extrusion can be used. Before extrusion forming, the mold and the blank are cooled to liquid nitrogen temperature, and the number of extrusion passes is greater than 6 times to prepare nano-level ultrafine grain structure, and the product processing quality can reach sub-nanometer level.

Claims

1. A die for preparing optical aluminum alloy by twisting, extrusion and large plastic deformation, characterized in that: include: A base, wherein a first discharge channel and a second discharge channel are formed on the base; The core mold sleeve and the core mold are arranged on the base, and the core mold is provided with a forward core mold and a reverse core mold which are connected with the first discharge channel and the second discharge channel. The forward core mold and the reverse core mold include spiral cylindrical channels with equal diameters, and the spiral directions of the forward core mold and the reverse core mold are opposite to offset the lateral force; An upper mold is arranged on the top of the core mold sleeve and the core mold; The extrusion rod seat assembly includes an extrusion rod seat and a first extrusion rod and a second extrusion rod arranged on the top of the upper mold; the extrusion rod seat and the upper mold are provided with a first extrusion channel and a second extrusion channel which are respectively connected to the forward core mold and the reverse core mold, and the first extrusion rod and the second extrusion rod move up and down in the first extrusion channel and the second extrusion channel to extrude the blank to be processed.

2. The die for preparing optical aluminum alloy by torsional extrusion and large plastic deformation according to claim 1, characterized in that: The base circle diameter of the spiral cylindrical channel of the forward core mold and the reverse core mold is 15mm-22mm, the pitch is 110mm-140mm, the helix angle is 18.6°-24.5°, and the number of spiral turns is 0.5-1.

3. The die for preparing optical aluminum alloy by torsional extrusion and large plastic deformation according to claim 1, characterized in that: The spiral cylindrical channel comprises a transition section connected to the upper and lower channels and an equal spiral section located between the two transition sections.

4. The die for preparing optical aluminum alloy by torsional extrusion and large plastic deformation according to claim 1, characterized in that: The forward core mold and the reverse core mold are inverted cone shapes, the shape of the core mold sleeve is matched with the forward core mold and the reverse core mold, and the forward core mold and the reverse core mold are fixed to the core mold sleeve through flat keys.

5. The die for preparing optical aluminum alloy by torsional extrusion and large plastic deformation according to claim 1, characterized in that: There is a 1-2mm gap between the forward core mold and the reverse core mold and the base, and the forward core mold and the reverse core mold are fitted with the upper mold.

6. A method for preparing an optical aluminum alloy using the mold according to any one of claims 1 to 5, characterized in that: include: Firstly, the blank is placed into the first extrusion channel and the second extrusion channel respectively; The blank is twisted and deformed in the spiral channel of the core mold by pressing down the extrusion rod, and the deformed blank is taken out from the outlets of the first discharge channel and the second discharge channel on the base; The deformed billet is put back into the first torsional extrusion channel and the second torsional extrusion channel, and the billet is pressed down again by the extrusion rod to cause torsional extrusion deformation in the spiral channel of the core mold. The torsional extrusion deformation operation is repeated to obtain an optical aluminum alloy product with large torsional plastic deformation. The billet diameter remains unchanged during the repeated operation.

7. The method for preparing an optical aluminum alloy according to claim 6, characterized in that: Before the blank is loaded into the mold, the mold release agent is evenly applied on the surface of the blank and then heated to a temperature of 250±10℃, and the mold is heated to a temperature of 250±10℃ at the same time; or Before the blank is loaded into the mold, a release agent is evenly applied on the surface of the blank and then heated to a temperature of 400-550°C, and at the same time the mold is heated to a temperature of 400-550°C.

8. The method for preparing an optical aluminum alloy according to claim 6, characterized in that: Before the blank is loaded into the mold, the mold and the blank are cooled to the temperature of liquid nitrogen, and the twisting and extrusion deformation operation is repeated for one blank more than 6 times.

9. The method for preparing an optical aluminum alloy according to claim 6, characterized in that: When the extrusion rod presses down to extrude the billet and cannot provide force on the current billet, the extrusion rod is removed, and new billets are loaded into the first extrusion channel and the second extrusion channel, and then the new billet is pressed down by the extrusion rod, and the new billet is used to extrude the previous billet out of the mold.

10. Use of a product obtained by the method for preparing an optical aluminum alloy according to any one of claims 6 to 9 in an optical reflector.

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